I think I know what's in the briefcase. "Memories" or at least something related. It fulfills the first few points of the riddle. They are a symbol of unity, friendship, and shared lives. Mistakes in your past can be brought back as memories. That fits the next few points. "Take as many as you need" says that there has to multiple of the object, so "Memories" seems fitting.

In the latest episode, there is mention of rings being flashed. We only see both hands fully of Cole, Hareka, and Aoke. I think that's an important note. Everyone else either has their hands in their pockets or wears gloves. Or they just keep their hands in an odd position to avoid showing. Just throwing it out there.

1. Try to keep everything family friendly.
2. Avoid swearing, cussing, NSFW stuff, etc.
3. Avoid drama with other people. We have private messages for a reason.
4. Refrain from spamming.
5. Don't troll people. There's no need for that kind of behavior in a fanclub for Static.
6. Have fun. That's the purpose of this club anyways.